A thermoplastic resin is formed by various methods, and is used as a formed product. Various forming methods are practically realized depending on the crystallinity, amorphous property, or melt viscosity, or shape of formed product, including injection forming, blow forming, extrusion forming, and press forming.
Depending on the type of the thermoplastic resin or the shape of formed products, the temperature of the thermoplastic resin may drop in the forming process, and the melt viscosity rises, and the desired formed product may not be obtained. As an improving method, it is proposed to heat the forming mold for forming a formed product by a heater or the like.
For example, in the resin forming method disclosed in patent document 1, the melted thermoplastic resin is cast into a cavity of a mold made of silicone rubber, and the thermoplastic resin is cooled, and a formed product is obtained. In order to obtain a resin formed product excellent in surface precision and surface gloss easily, the composition of the mold made of silicone rubber is modified.
In the conventional resin forming method, however, especially in an end portion of the cavity to be filled with the thermoplastic resin, the temperature of the thermoplastic resin to be formed is likely to decline, and the viscosity of the thermoplastic resin may be raised. In such a case, in the cavity of the mold, insufficient filling with the thermoplastic resin may occur.
In patent document 1, meanwhile, the heat resisting temperature of silicone rubber is about 200° C., and if the heating temperature by the heater or the like is raised in order to prevent decline of temperature of the resin, the mold of silicone rubber deteriorates, and the surface appearance of the formed product formed from this mold may be poor.
For example, in the manufacturing method and its apparatus of a resin formed product disclosed in patent document 2, in the process of obtaining a formed product by charging a granular or powder metal aggregate and the thermoplastic resin in a mold frame, metal heating means is used for heating the metal aggregate locally. In this manufacturing method, from the metal heating means, microwaves or electromagnetic waves are irradiated to the metal aggregate in the mold frame, and the metal aggregate is heated, and the generated heat from the metal aggregate is utilized for softening or melting the thermoplastic resin in the mold frame, and the resin formed product is pressed and formed.
However, the technology in patent document 2 is a technology of heating the metal aggregate selectively, not heating the thermoplastic resin itself. Further, by the metal heating means, the mold frame is also heated when heating the metal aggregate. Therefore, the thermoplastic resin only cannot be heated selectively without heating the mold frame substantially.
For example, patent document 3 discloses a forming method of filling with the thermoplastic resin by vacuum injection method.    Patent document 1: JP 7-178754 Examined Patent Publication (Kokoku)    Patent document 2: JP 10-193370 Examined Patent Publication (Kokoku)    Patent document 3: JP 2002-59468 Examined Patent Publication (Kokoku)